Electric immersion heater

ABSTRACT

An electric immersion heater for use with home aquarium tanks. A glass tube containing at the bottom thereof an electric heating element is yieldably suspended within and in spaced relation to a heat-resisting apertured casing, the casing having a cover member with a depending bar extending into the tube and supporting the terminals of a thermostat. The casing and its said cover member have two complementary lateral extensions together forming a channelled passageway for electric conductors extending into the tube and connected to said terminals, said heating element being connected in series with said thermostat, there being a fuse in adjacent relation to and connected in series with said heating element. A knob member is rotatably mounted over said cover member and has a control rod in threaded engagement with the latter, the rod extending down into the tube and being operatively engageable with a contact arm of said thermostat, said knob being engageable with said cover member and thereby serving as a stop to prevent the control rod from excessively bending the engaged thermostat contact arm.

United States Patent [72] inventors Anthony N. DElia New York; Edward M.Stolarz, Yorktown Heights, both of N.Y. [21] Appl. No. 65,132 [22] FiledAug. 19, 1970 [45] Patented Nov. 9, 1971 [73] Assignee SterncoIndustries, Inc.

Harrison, NJ.

[541 ELECTRIC IMMERSION HEATER 7 Claims, 6 Drawing Figs.

[52] 11.8. C1 219/523, 219/328, 219/336, 219/337, 219/517 [51] Int. ClH05b 3/06, H05b 3/08, H05b 3/02 [50] Field ofSearch 219/523, 322, 328,336-337, 517, 437

[56] References Cited UNITED STATES PATENTS 2,507,750 5/1950 Barlow219/523 X 2,811,629 10/1957 Danner... 219/523 3,107,290 10/1963Willinger 219/523 X 3,476,915 11/1969 Rapsis 3,564,589 2/1971 ArakABSTRACT: An electric immersion heater for use with home aquarium tanks.A glass tube containing at the bottom thereof an electric heatingelement is yieldably suspended within and in spaced relation to aheat-resisting apertured casing, the casing having a cover member with adepending bar extending into the tube and supporting the terminals of athermostat. The casing and its said cover member have two complementarylateral extensions together forming a channelled passageway for electricconductors extending into the tube and connected to said terminals, saidheating element being connected in series with said thermostat, therebeing a fuse in adjacent relation to and connected in series with saidheating element. A knob member is rotatably mounted over said covermember and has a control rod in threaded engagement with the latter, therod extending down into the tube and being operatively engageable with acontact arm of said thermostat, said knob being engageable with saidcover member and thereby serving as a stop to prevent the control rodfrom excessively bending the engaged thennostat contact arm.

ELECTRIC IMMERSION HEATER BACKGROUND OF THE INVENTION 1. The Field ofthe Invention This invention relates to electric immersion heaters, andis especially directed to portable heaters of this class adapted for usewith home aquarium tanks.

2. The Known Art The known thermostatically controlled devices in thiscategory, while capable of heating water and maintaining it atpredetermined temperatures, do not contain certain safety features, orcombinations of such features, deemed necessary for underwritersapproval when used with a home aquarium. This type of heater is almostalways intended for manual handlingsuch as attaching the device to thewall of an aquarium tank and removing it when cleaning the tank or whenit is desired to examine the device for one reason or another. Duringsuch operations the conventional glass tube containing the heatingelement is frequently subjected to shocks and impacts due tomishandling, with the consequent danger of breakage of the tube ordisplacement of the delicate parts of the enclosed heating elementthermostat. It is also a common occurrence for the device to be removedfrom the tank, while the circuit is still closed, and placed upon atable or other supporting surface. Since the device is no longer cooledby surrounding water, the temperature of the portion of the glass tubeimmediately adjacent the heating element may become sufficiently high toscorch the supporting surface or any adjacent infalmmable material, thedevice thus constituting a fire hazard. It also frequently happens withconventional immersion heaters that when the device is temporarilyremoved from the tank for a brief inspection or adjustment withoutturning off the current, the fuse in the line may blow after a veryshort interval in the air-beforethe device could be returned to thetank-asituation that is quite apt to arise where the line is subject tocurrent fluctuations. Another disadvantage of conventional immersionheaters having thermostats that are intended to be hand adjusted is theever present danger that during the adjusting manipulation the coactivethermostatic contact elements, or the bimetallic element thereof, mayinadvertently be bent an excessive amount, thereby distorting theelement or elements and destroying their operative effectiveness.

OBJECTS OF THE INVENTION It is the objective of this invention toprovide an immersion heater adapted especially for use with homeaquariums that will function effectively and safely, and that will havenone of the shortcomings abovementioned. More specifically, among theobjects of this invention are the following: to provide means forprotecting the heating element, its glass tube enclosure and thecoactive elements therein against excessive shock and impact effects; toprovide such protection and at the same time permit the heating memberto be effectively immersed in and in engagement with the water beingheated; to provide adequate sealing means for the tube, its contents andthe electric wiring within the device; to provide a heat-resistingbarrier around the tube, especially the portion thereof immediatelyadjacent the heating element, thereby to prevent scorching oroverheating of a surface upon which the device is placed when it istaken out of the water; to provide a thermostat with a hand-adjustingmeans having stop means thereon to prevent any excessive bending ordistortion of the thermostat elements; to provide lighting means toindicate whether the device is operatively electrically connected; toprovide a fuse in such proximate relation to the heating element as tobe operatively effective as soon as the tube air surrounding the heatingelement reaches a predetermined temperature; and to arrange said fuseand a thermostat in such predetermined spaced relation to the heatingelement and of such functional the air during a predetermined period oftime before the fuse blows.

SUMMARY OF THE INVENTION In the preferred form of this invention, anelongated glass tube containing at the lower portion thereof aconventional electrical heating element is held suspended within anelongated casing of heat-resisting plastic material, the lateralapertured wall of the casing surrounding said tube and being in spacedrelation thereto. The upper part of the casing contains an inner annularshoulder supporting a soft bushing of insulating material, the upperportion of the tube, which is open at the top, being in pressingcircumferential engagement with said bushing, the top of the tube havinga peripheral lip embedded in the bushing, whereby the tube is yieldablysupported in its suspended position.

In sealing engagement with the top of the casing and the upper surfaceof the bushing is a cover member of heat and electrical insulatingproperties and having an upwardly extending central portion ofsubstantially frustoconical configuration, the top horizontal wall ofthe cover member having a vertical axially disposed threaded aperturedportion. Said cover member has a horizontally extending portionoverlying and in engagement with a corresponding portion extending fromthe top of said casing, both of said extending portions forming a sealedpassageway for electric conductors operatively connected to the tube 5heating element and associated parts. The said cover member also has anintegral inner bar depending downwardly therefrom into the tube, the barsup porting two spaced electric terminals operatively connected to thetwo coactively positioned contact-supporting arms of a thermostat, therebeing conductors connecting said thermostat and the electric heatingelement in series, and a lamp in parallel.

Rotatably positioned over the said frustoconical portion of said covermember is a correspondingly shaped knob; and extending downwardly andaxially therefrom is a thermostat control rod extending through andbeing in threaded engagement with said threaded aperture portion of saidcover member, the bottom end of said rod being in abutting engagementwith the upper of said thermostat arms for controlling the frequency ofthe make and break action of the said arms in known manner. In order toprevent an excessive bending and permanent distortion of said arms, thesaid knob is so proportioned and positioned with respect to the top ofsaid cover member and the bottom end of the control rod that the knobengages the top of the cover member when the said bottom end of the rodis at a predetermined level above that at which the said thermostatarms, or either of them, is excessively bent-the top of the cover memberstopping any further downward movement of the control rod.

An extremely important feature of this invention is the use of a fusepositioned in proximate relation to and above the electric heatingelement. As will more clearly hereinafter appear, the spaced relation ofthe closely positioned fuse and remotely positioned thermostat withrespect to the heating element, and their respective electrical andphysical characteristics, are such as to provide a predetermined safeminimum temperature spread between the tube air temperature when thedevice is in water and its temperature when in air, so that when thedevice is in air with the current on, the danger of the fuse blowingbefore a predetermined time will be reduced to a minimum. The spacing ofthe outer casing wall from the glass tube is such that the ventilatedspace between the tube and casing, as well as the heat-resistingproperties of the casing material, will obviate the danger of theportion of the casing immediately adjacent the heating element frombecoming dangerously hot before the time set for the fuse to blow.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical longitudinal section ofan embodiment of this invention, portions being shown in frontelevation, the thermostat control rod being in its lowest position.

FIG. 2 is a fragmentary front elevation of the device of FIG. I, aportion being broken away and showing the position of the contact armsof the thermostat with the control rod in a raised position.

FIG. 3 is a fragmentary section of FIG. 1 taken along line 3-3, withportions removed for clarity.

FIG. 4 is a fragmentary side elevation of FIG. 1.

FIG. 5 is a top view of FIG. 1, shown partly in section.

FIG. 6 is a top view of the device with cover and knob portions removed.

DESCRIPTION OF A PREFERRED EMBODIMENT In the illustrated embodiment ofthe immersion heater constituting this invention, a tubular casing 10 ofheat-resisting plastic material supports therein the tubular member 11,shown as a glass tube, containing at the lower portion thereof theelectric heating element 12 of conventional construction, said tube andheating element being collectively referred to herein as the heatingmember 13. The lateral wall 14 of said casing 10 is in spaced relationto said tube Ill and is provided with a plurality of apertures 15, thearrangement being such as to permit the water into which the device isoperatively immersed to course through the apertures 15 and move (byconvection) through the space 16 for effective engagement with theheating member 13, as well as to permit air circulation within saidspace 16 when the device is taken out of the water, thereby to helpinsulate the wall 14 of the casing from the heating element 12.

The upper portion of the casing 10 has a thickened annular wall portion17 with a depressed annular shoulder 18 to receive the top flange 19 ofthe bushing 20 made of soft, resilient, water-impervious material, thegenerally cylindrical body portion 21 of said bushing being in yieldablepressing engagement with the adjacent inner surface of said thickenedwall portion 17 and the adjacent outer surface of the glass tube 11, thetop open portion 22 of the tube having the peripheral lip 23 in pressingengagement with the top of said bushings flange 19, the upper portion ofsaid flange being in pressing engagement with the cover member 33 to behereinafter described.

The arrangement is such that said glass tube 11 is yieldably heldsuspended within said casing I0, the entire tube below the casings saidthickened portion 17 being in spaced relation to the casing's wall 14.The top of the casing is also provided with a lateral extension 24having therein a channel 25a to accommodate therein electricalconductors for connection to a source of current supply, as will moreclearly hereinafter appear. The said extension 24 has dependingtherefrom the wall section 26 having a threaded aperture 27 throughwhich extends the threaded shank 28 of the clamping knob 29, theterminal 30 being adapted for holding engagement with the top rim of anaquarium, such as the illustrated rim 31 of the aquarium wall 32,whereby the casing 10 and associated parts are operatively supported, inknown manner, within the interior of an aquarium.

Mounted over and in sealed relation to the said casing 10 is the saidcover member 33, made of heat-resisting and electrical insulatingmaterial, said member having an upwardly extending central portion 34preferably, although not necessarily, of substantially frustoconicalconfiguration. The top wall 35 of said cover member has an axialvertically disposed threaded apertured portion 36 in threaded engagementwith the thermostat control rod 37 to be hereinafter described. Saidcover member 33 has a lateral extension 38 proportioned to correspondwith said extension 24 of the casing, extension 38 overlying saidextension 24 and having a channel 25b overlying said channel 2511,thereby forming the channel 25, through which the conductor wire 39extends, the outer portion of said wire being adapted for connection toa wall outlet. In the preferred embodiment illustrated said channel 25contains a seal 40 of suitable material in engagement with the surfaceof said wire 39 and the walls of the said channel to prevent water fromentering the tube 11 into which the conductor leads 39a and 39b extend.I

Rotatably positioned over the said frustoconical portion 34 of the covermember 33 is the knob 41 having a correspondingly shaped hollowfrustoconical portion 42 from the top wall 43 of which depends the saidthermostat control rod 37. The bottom end 44 of said rod is in abuttingengagement with the upper contact arm 45 of the thermostat generallydesignated 46, the bimetallic contact arm 47 being in coacting relationto said arm 45 in known manner, said contact arms extending transverselywithin the upper portion of said tube 11. The said lead 390 is connectedto the terminal 48 of said contact arm 45, the other lead 3% beingelectrically connected by conductor 49 to said heating element 12, thelatter being electrically connected by the conductor 50 to the terminal51 of said bimetallic contact arm 47. Both of said terminals 4B and 51are affixed to the bar 52 which is integral with said cover member 33and extends downwardly therefrom into said tube 11, said contact arms 45and 47 being supported by said bar 52.

In the particular construction illustrated, the shape of the annularwall 53 of the knob 41 conforms to that of the said upwardly extendingcentral portion of the cover member 33, and is abuttable therewith whensaid bottom end 44 of the thermostat control rod 37 reaches apredetermined low limiting position upon an operative rotation of theknob 41 so that there could be no further downward movement of the rod.The said predetermined low level is that at which the rod will notexcessively bend the contact arms 45 and 47, or either of them, topositions at which they will become permanently distorted or incapableof effectively performing their intended functions. The said knob 41accordingly serves not only to adjust the make-and-break action of saidthermostat anns 45 and 47 for maintaining, in known manner, the water atthe desired temperature, but also serves as a stop to prevent destroyingthe functional usefulness of the thermostat by careless operativemanipulation of the control knob.

The said bar 52 is, as aforesaid, a part of the cover member 33 which isadjacent the top of the tube 11, the heating element 12 being at theopposite end thereof-the arrangement being such that the thermostat 46is remotely situated from the heating element. In relatively proximaterelation to the heating element is the fuse 54 connected to theconductor 50 and in series with the thermostat 46.

If the device is taken out of the water, with the current on and thethermostat switch closed, the casing 10, especially the portion thereofimmediately adjacent the heating element 12, will be subjected toincreasing heat effects due to the absence of water until the fuseblows; but due to the apertured wall 14 spaced from the tube 11, thisprogressively increasing heating action is reduced through theventilating and insulating action of the air within the space 16surrounding the tube. With this heat-retarding effect, the fuse 54 isset to blow after a predetermined reasonably sufficient time for thedevice to be held in the air (for inspection, cleaning, or otherpurpose) prior to being returned to the water. If it is held in the airfor a longer period, say longer than 3 minutes, the fuse, being close tothe heating element, will blow immediately as the air in the tubeadjacent the heating element reaches a predetermined temperature, sayF., at which the portion of the casing adjacent the heating elementbecomes too hot for safety. It is, however, also important that thespread between the temperature attained by the tube air in the regionadjacent the thermostat with the device in water and the fuse-blowingtemperature with the device withdrawn from the water be not too small,since under such a condition current fluctuations might cause anunwanted blowing of the fuse. With the fuse close to the heating elementand the thermostat remote therefrom, with both fuse and thermostat,being operatively reactive to the temperature of the air within thetube, and with a ventilating space between the tube 11 and the casing10, it has been found that a reasonably safe spread can be obtainedbetween said device-in-water and device-in-air temperatures.

In the illustrated device the casing I0 has an aperture 55 in the casingadjacent the lamp 56 connected in parallel to the heating element 12,thereby to indicate whether the device is heating.

It will be observed that the fragile tube 11 is yieldably suspendedwithin the casing and maintained in spaced relation to the tube by theresilient bushing 20. Any impact the device will suffer due tomishandling will accordingly be cushioned, with minimum danger ofbreakage of the tube or dislodgment of its delicate contents. Should thedevice be placed on a supporting surface with the current on, theheatinsulating air between the casing and the tube will obviate thedanger of scorching the supporting surface or adjacent flammablematerial.

in the above description, the invention has been disclosed merely by wayof example and in preferred manner; but obviously many variations andmodifications may be made therein. it is to be understood, therefore,that the invention is not limited to any particular form or manner ofpracticing same.

We claim:

1. An electric immersion heater comprising a tubular heating memberhaving a heating element therein, a casing of heatresisting materialsurrounding and in spaced relation to said tubular member, resilientmeans between and in pressing engagement with the upper portions of saidtubular member and casing for yieldably supporting said member withinthe casing, a cover member in sealing engagement with the top of saidcasing and having a downwardly depending bar extending into said tubularmember, a thermostat having coactive contact arms supported by said barand disposed within said tubular member, said casing and cover memberhaving lateral extensions in coactive relation and together forming aninternal passageway for electric conductors, a pair of electricconductors within said passageway, a knob in rotatable engagement withthe top of said cover member and having a thermostat control rodextending downwardly through and in threaded engagement with said covermember, said control rod being in engagement with one of said contactarms for operatively adjusting the relative positions of said arms, saidknob having a wall portion engageable with an underlying wall portion ofsaid cover member at a predetermined low limiting position of saidcontrol rod, said heating element being electrically connected tosaidthermostat and said conductors, and a fuse in adjacent relation to saidheating element and disposed between and connected in series with saidheating element and said thermostat.

2. An electric immersion heater according to claim 1, said bar havingthereon two terminals electrically connected to said respective contactarms, said heating element being con nected to one of said terminals andto one of said conductors, the other of said conductors being connectedto the other of said terminals.

3. An electric immersion heater according to claim 1, said resilientmeans comprising a flanged bushing of soft yieldable material imperviousto water, the upper part of said casing having a thickened annularportion with a recessed annular shoulder supporting the flanged portionof said bushing, said cover member being in pressing and sealingengagement with the said flanged portion.

4. An electric immersion heater according to claim 1, said casing havingapertured portions in the wall thereof, an electric lamp within saidtubular member and connected in parallel to said heating element, one ofsaid apertured portions being in registry with said lamp for visualobservation.

5. An electric immersion heater according to claim 1, the said lateralextension of the casing having a depending wall portion, a holding knobmember having a shank in threaded engagement with said depending wallportion and adapted for abutting engagement with the rim of an aquariumtank.

6. An electric immersion heater according to claim 1, said cover memberhaving an upwardly extending central portion containing a threadedapertured portion, said knob having a hollow portion defined by a wallportion of a configuration complementary to that of said centralportion, said control rod extending down from the central axial portionof said knob and having a portion thereof in threaded engagement withsaid threaded apertured portion, said wall portion of said knob beingeng cable with said upwardl extending central portion of sar covermember when sat control rod rs in its said low limiting position.

7. An electric immersion heater according to claim 6, said upwardlyextending portion of the cover member being of substantiallyfrustoconical configuration, and said complementary wall portion of saidknob being of corresponding substantially frustoconical configuration,whereby the correspondingly positioned frustoconical portions of saidcover member and knob will be in abutting engagement when said controlrod is in its said low limiting position.

1. An electric immersion heater comprising a tubular heating memberhaving a heating element therein, a casing of heatresisting materialsurrounding and in spaced relation to said tubular member, resilientmeans between and in pressing engagement with the upper portions of saidtubular member and casing for yieldably supporting said member withinthe casing, a cover member in sealing engagement with the top of saidcasing and having a downwardly depending bar extending into said tubularmember, a thermostat having coactive contact arms supported by said barand disposed within said tubular member, said casing and cover memberhaving lateral extensions in coactive relation and together forming aninternal passageway for electric conductors, a pair of electricconductors within said passageway, a knob in rotatable engagement withthe top of said cover member and having a thermostat control rodextending downwardly through and in threaded engagement with said covermember, said control rod being in engagement with one of said contactarms for operatively adjusting the relative positions of said arms, saidknob having a wall portion engageable with an underlying wall portion ofsaid cover member at a predetermined low limiting position of saidcontrol rod, said heating element being electrically connected to saidthermostat and said conductors, and a fuse in adjacent relation to saidheating element and disposed between and connected in series with saidheating element and said thermostat.
 2. An electric immersion heateraccording to claim 1, said bar having thereon two terminals electricallyconnected to said respective contact arms, said heating element beingconnected to one of said terminals and to one of said conductors, theother of said conductors being connected to the other of said terminals.3. An electric immersion heater according to claim 1, said resilientmeans comprising a flanged bushing of soft yieldable material imperviousto water, the upper part of said casing having a thickened annularportion with a recessed annular shoulder supporting the flanged portionof said bushing, said cover member being in pressing and sealingengagement with the said flanged portion.
 4. An electric immersionheater according to claim 1, said casing having apertured portions inthe wall thereof, an electric lamp within said tubular member andconnected in parallel to said heating element, one of said aperturedportions being in registry with said lamp for visual observation.
 5. Anelectric immersion heater according to claim 1, the said lateralextension of the casing having a depending wall portion, a holding knobmember having a shank in threaded engagement with said depending wallportion and adapted for abutting engagement with the rim of an aquariumtank.
 6. An electric immersion heater according to claim 1, said covermember having an upwardly extending central portion containing athreaded apertured portion, said knob having a hollow portion defined bya wall portion of a configuration complementary to that of said centralportion, said control rod extending down from the central axial portionof said knob and having a portion thereof in threaded engagement withsaid threaded apertured portion, said wall portion of said knob beingengageable with said upwardly extending central portion of said covermember when said control rod is in its said low limiting position.
 7. Anelectric immersion heater according to claim 6, said upwardly extendingportion of the cover member being of substantially frustoconicalconfiguration, and said complementary wall portion of said knob being ofcorresponding substantially frustoconical configuration, whereby thecorrespondingly positioned frustoconical portions of said cover memberand knob will be in abutting engagement when said control rod is in itssaid low limiting position.